CBSE Class 12 Biology 2026 question paper (57/1)

Maximum marks 70 · Time 3 hours · 3 sets

Try each question first, then open its model answer. Where the paper offers a choice, both questions are shown with OR between them.

Section A

1 mark each

Q.11 mark $Identify the plant in which emasculation is not required for artificial hybridization.$
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Q.21 mark $Which of the following is not a component of immune system ?$
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Q.31 mark $Select the option that shows correct statements : (i) Corpus luteum secretes progesterone. (ii) Only FSH attains a peak level in middle of cycle. (iii) LH surge induces rupture of graafian follicle. (iv) Luteal phase of menstrual cycle is also called proliferative phase.$
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Q.41 mark $Select the mismatched pair :$
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Q.51 mark $Pomato was produced by fusing protoplasts of$
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Q.61 mark $In an ecosystem, different species occupy different levels and vertical distribution of species is found. This is called _________.$
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Q.71 mark $Which of the following sacred groves is found in Meghalaya ?$
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Q.81 mark $In the following figure, two ways of pairing of two homologous pairs of chromosomes are shown. Which of the following phenomena is expressed ?$
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Q.91 mark $\text{Ca}^{++}$
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Q.101 mark $The idea of use and disuse of organs for evolution of organism was proposed by$
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Q.111 mark $Which of the following statements about plasmids is incorrect ?$
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Q.121 mark $Which connective tissue connects ovary to pelvic wall and uterus ?$
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For Questions number 13 to 16, two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) given below :
Q.131 mark $Assertion (A) : The population of melanized moths increased in industrial areas after Industrial Revolution. Reason (R) : In Industrial environment lichen covered trees were replaced by soot-covered trees offering better camouflage to dark coloured moths.$
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Q.141 mark $Assertion (A) : The milk produced by transgenic cow 'Rosie' was nutritionally more balanced product for human babies than natural cow milk. Reason (R) : It was human protein enriched milk containing human alpha lactaglobulin.$
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Q.151 mark $Assertion (A) : Flocs are masses of bacteria associated with fungal filaments in secondary treatment of sewage. Reason (R) : Flocs help in digestion of solid waste by anaerobic respiration.$
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Q.161 mark $Assertion (A) : In terrestrial ecosystem much larger fraction of energy flows through grazing food chain. Reason (R) : Grazing food chain may be connected to Detritus food chain at some levels.$
Tap an option to check your answer.

Column-I	Column-II
a. Biolistic gun	i. Bacterial cell
b. Chitinase	ii. Tumour inducing
c. Ti	iii. Animal cell
d. $\text{Ca}^{++}$	iv. Fungal cell
	v. Plant cell

Section B

2 marks each

Q.172 marks $(a) Define Humoral immune response. (b) Name any two types of antibodies found to give humoral immune response in humans.$
Q.18 (a)2 marks $(i) How does a farmer use dormancy of seed to his advantage ? (ii) Differentiate between pea seed and castor seed.$
OR
Q.18 (b)2 marks $Identify the stage of follicle where primary oocyte undergoes first meiotic division. Also mention the products of this division.$
Q.192 marks $Study the sequence of bases in a DNA molecule that is shown below and answer the questions. 5' - GAATTC - 3' 3' - CTTAAG - 5' (a) What are such sequences called ? Name the enzyme used that recognises such nucleotide sequences. (b) How do these enzymes function ?$
Q.20 (a)2 marks $Analyse the following two cases of sex determination in different organisms : Case I : Males have (XO) sex chromosomes and females have two copies of same sex chromosome (XX). Case II : Females have two different sex chromosomes (ZW) and males have two copies of same sex chromosome (ZZ). Identify the type of heterogamety in each case, giving one example of each.$
OR
Q.20 (b)2 marks $(i) Differentiate between a DNA and RNA nucleotide. (ii) Name the two types of bonds present within a single nucleotide.$
Q.21 (a)2 marks $Given below is a pyramid found in an ecosystem, where each bar represents the standing crop available in the trophic level. (i) Identify the kind of pyramid and with the help of an example explain the conditions where this kind of pyramid is possible in nature. (ii) Write any two limitations of ecological pyramids.$
OR
Q.21 (b)2 marks $In an ecosystem there was loss of biodiversity due to some project in that area. (i) How will biodiversity be affected ? (2 points) (ii) List two major causes of loss of biodiversity.$

Section C

3 marks each

Q.223 marks $(a) Do all pollen grains remain viable for the same length of time ? Support your answer with two suitable examples. (b) How are pollen grains stored in pollen banks ?$
Q.233 marks $(a) What is pedigree analysis ? Mention its importance in human genetics. (2 pts.) (b) Analyse the following pedigree and write the (i) Pattern of inheritance. (ii) Give one example of disease showing such an inheritance pattern.$
Q.243 marks $(p^2 + 2pq + q^2) = 1$
Q.253 marks $Draw a neat diagram of megasporangium of an angiosperm and label any six parts.$
Q.263 marks $(a) Mention the scientific name of the source plant and the part from which opioids are extracted. (b) How are morphine and heroin related ? Mention the effect each one of them has on human body.$
Q.273 marks $A farmer grew two varieties of corn crop in field A and B. He grew normal corn crops in field A and GM corn crops in field B. He observed that corn borers attacked only in field A. To control it, spores of Bt were sprayed on field A. (a) Name the gene in the spores responsible for control of pest. (b) What effect will the spores of Bt have on insect pest ? (c) How has corn plants of field B developed resistance against this pest ? Explain.$
Q.283 marks $Observe the given picture carefully. A mixture of DNA with fragments ranging from 100 base pairs to 1800 base pairs were separated by electrophoresis on agarose gel with the following arrangement : (a) What result will be obtained in staining with ethidium bromide ? Explain with reasons. (b) The above setup was modified as shown below and a band with 100 base pairs was obtained at X. What changes were made to the previous design to get a band at 'X'. Why did the band appear at 'X' ?$

Section D

The diagram below shows the distribution of two barnacle species, Chthamalus and Balanus on a rocky sea shore. When Balanus is experimentally removed, Chthamalus expands its range in lower intertidal zone.
Q.29 (a)1 mark $Identify and define the ecological phenomenon demonstrated by this observation.$
OR
Q.29 (a) OR1 mark $State the principle that explains the elimination of one species.$
Q.29 (b)1 mark $Two different species can compete for the same resource. Give another example of it.$
Q.29 (c)2 marks $How do species avoid competition in nature ? Explain with an example.$
A student performed some crosses in plants and represented the result in the form of bar graphs as shown below. Each graph displays the phenotypic proportion of the progeny. Study the graphs and answer the questions :
Q.30 (a)1 mark $What can you infer about the genotype of parents in crosses I and II ?$
OR
Q.30 (a) OR1 mark $Which genetic cross is represented by these crosses ?$
Q.30 (b)2 marks $Looking at bar graph of cross III, identify the type of cross performed and its importance in genetics.$
Q.30 (c)1 mark $What conclusion can you draw from the results of bar graphs of crosses I and II ? Name the genetic principle illustrated.$

Section E

5 marks each

Q.31 (a)5 marks $Trace the events from fertilization till implantation of blastocyst in human female. Also mention the site where fertilization takes place.$
OR
Q.31 (b)5 marks $(i) Case studies of some couples are given below. They were not able to have kids even though the parents were not taking any precautions. They also do not wish to adopt a child or take the help of donors. Study these cases and suggest an appropriate Assisted Reproductive Technology that could help them. Case I - Female - Normal Reports Male - Normal sperms but no connection between epididymis and vas deferens. Case II - Female - Normal eggs but Fallopian tube blocked. Male - Normal sperms. Male reports are normal. Case III - Female - Normal Reports. Male - Low sperm count with less motility. (ii) Copper releasing intrauterine devices are very effective and popular contraceptive devices. Name any two copper releasing IUDs. Write two reasons that make them effective contraceptives.$
Q.32 (a)5 marks $(i) Watson and Crick's discovery of double helical structure was based on which two findings. Also mention the name of the scientists associated with these findings. (ii) Write down the salient features of double helix structure of DNA (any three points).$
OR
Q.32 (b)5 marks $Given below is a stretch of DNA showing the coding strand of structural gene of transcription unit. 5' - ATG ACC GTA TTT TCT GTA GTG CCC GTA CTT CAG GCA TTA 3' (i) Write the corresponding template strand and m-RNA strand that will be transcribed along with its polarity. (ii) If GUA of transcribed mRNA is an intron, then depict the sequence involved in formation of mRNA / mature / processed hnRNA strand : (1) In a bacterium (2) In humans (iii) How many amino acids the resulting polypeptide will have after the process of translation in humans ?$
Q.33 (a)5 marks $(i) Name the protozoan species that is responsible for causing the most serious and even fatal malarial disease. (ii) Name the host in which the parasite completes its sexual stages and explain the changes taking place. (iii) How does the parasite damage the human body after entering the blood stream ? (iv) Suggest two effective preventive measures to control the spread of this disease in endemic regions.$
OR
Q.33 (b)5 marks $(i) What are bio-fertilizers ? (ii) Name the different types of microorganisms used as bio-fertilizers in organic farming and explain how each contributes to soil fertility. (iii) Write two advantages of using bio-fertilizers over chemical fertilizers.$

Section A

1 mark each

Q.11 mark $\text{Ca}^{++}$
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Q.21 mark $Microbes commonly used in kitchen are$
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Q.31 mark $The features of some structures of human male reproductive system are given below. Choose the correct option that matches the features with the structures. (i) It opens into the Vasa efferentia through rete testis. (ii) It carries semen as well as urine. (iii) It maintains temperature (2 - 2.5°C) lower than body temperature for sperm formation. (iv) It leads to vas deferens that ascends to the abdomen.$
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Q.41 mark $Exploration of molecular, genetic and species level diversity for gaining products of economic importance is called$
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Q.51 mark $Which connective tissue connects ovary to pelvic wall and uterus ?$
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Q.61 mark $Which of the following is not a component of detritus food chain ?$
Tap an option to check your answer.
Q.71 mark $Identify the plant in which emasculation is not required for artificial hybridization.$
Tap an option to check your answer.
Q.81 mark $Pomato was produced by fusing protoplasts of$
Tap an option to check your answer.
Q.91 mark $Which of the following sacred groves is found in Meghalaya ?$
Tap an option to check your answer.
Q.101 mark $\text{CsCl}_2$
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Q.111 mark $Which one of the following is not a component required for Polymerase Chain Reaction (PCR) ?$
Tap an option to check your answer.
Q.121 mark $In the following figure, two ways of pairing of two homologous pairs of chromosomes are shown. Which of the following phenomena is expressed ?$
Tap an option to check your answer.
For Questions number 13 to 16, two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) given below :
Q.131 mark $Assertion (A) : When we see stars, we are apparently peeping into the past. Reason (R) : What we see today is an object whose emitted light started its journey millions of years back reaching our eyes now.$
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Q.141 mark $Assertion (A) : Flocs are masses of bacteria associated with fungal filaments in secondary treatment of sewage. Reason (R) : Flocs help in digestion of solid waste by anaerobic respiration.$
Tap an option to check your answer.
Q.151 mark $Assertion (A) : In terrestrial ecosystem much larger fraction of energy flows through grazing food chain. Reason (R) : Grazing food chain may be connected to Detritus food chain at some levels.$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : The milk produced by transgenic cow 'Rosie' was nutritionally more balanced product for human babies than natural cow milk. Reason (R) : It was human protein enriched milk containing human alpha lactaglobulin.$
Tap an option to check your answer.

Column-I	Column-II
a. Biolistic gun	i. Bacterial cell
b. Chitinase	ii. Tumour inducing
c. Ti	iii. Animal cell
d. $\text{Ca}^{++}$	iv. Fungal cell
	v. Plant cell

Section B

2 marks each

Q.172 marks $(a) What is the role of LAB (Lactic Acid Bacteria) in preparation of curd ? (b) Mention two health benefits of consuming curd.$
Q.18 (a)2 marks $Name the muscular and glandular layers of female uterus. Mention one function of each.$
OR
Q.18 (b)2 marks $(i) Why are STI (Sexually Transmitted Infections) not detected in time ? (2 pts.) (ii) Write two complications caused in later stages.$
Q.192 marks $Write the importance of following in biotechnology : (a) Ori (Origin of Replication) (b) Enzyme Polymerase used in Polymerase Chain Reaction$
Q.20 (a)2 marks $Given below is a pyramid found in an ecosystem, where each bar represents the standing crop available in the trophic level. (i) Identify the kind of pyramid and with the help of an example explain the conditions where this kind of pyramid is possible in nature. (ii) Write any two limitations of ecological pyramids.$
OR
Q.20 (b)2 marks $In an ecosystem there was loss of biodiversity due to some project in that area. (i) How will biodiversity be affected ? (2 points) (ii) List two major causes of loss of biodiversity.$
Q.21 (a)2 marks $Analyse the following two cases of sex determination in different organisms : Case I : Males have (XO) sex chromosomes and females have two copies of same sex chromosome (XX). Case II : Females have two different sex chromosomes (ZW) and males have two copies of same sex chromosome (ZZ). Identify the type of heterogamety in each case, giving one example of each.$
OR
Q.21 (b)2 marks $(i) Differentiate between a DNA and RNA nucleotide. (ii) Name the two types of bonds present within a single nucleotide.$

Section C

3 marks each

Q.223 marks $A farmer grew two varieties of corn crop in field A and B. He grew normal corn crops in field A and GM corn crops in field B. He observed that corn borers attacked only in field A. To control it, spores of Bt were sprayed on field A. (a) Name the gene in the spores responsible for control of pest. (b) What effect will the spores of Bt have on insect pest ? (c) How has corn plants of field B developed resistance against this pest ? Explain.$
Q.233 marks $Observe the given picture carefully. A mixture of DNA with fragments ranging from 100 base pairs to 1800 base pairs were separated by electrophoresis on agarose gel with the following arrangement : (a) What result will be obtained in staining with ethidium bromide ? Explain with reasons. (b) The above setup was modified as shown below and a band with 100 base pairs was obtained at X. What changes were made to the previous design to get a band at 'X'. Why did the band appear at 'X' ?$
Q.243 marks $(a) Mention the scientific name of the source plant and the part from which opioids are extracted. (b) How are morphine and heroin related ? Mention the effect each one of them has on human body.$
Q.253 marks $Give the schematic representation of oogenesis in human female. Indicate chromosome number also.$
Q.263 marks $(a) Do all pollen grains remain viable for the same length of time ? Support your answer with two suitable examples. (b) How are pollen grains stored in pollen banks ?$
Q.273 marks $(a) What is pedigree analysis ? Mention its importance in human genetics. (2 pts.) (b) Analyse the following pedigree and write the (i) Pattern of inheritance. (ii) Give one example of disease showing such an inheritance pattern.$
Q.283 marks $(p^2 + 2pq + q^2) = 1$

Section D

A student performed some crosses in plants and represented the result in the form of bar graphs as shown below. Each graph displays the phenotypic proportion of the progeny. Study the graphs and answer the questions :
Q.29 (a)1 mark $What can you infer about the genotype of parents in crosses I and II ?$
OR
Q.29 (a) OR1 mark $Which genetic cross is represented by these crosses ?$
Q.29 (b)2 marks $Looking at bar graph of cross III, identify the type of cross performed and its importance in genetics.$
Q.29 (c)1 mark $What conclusion can you draw from the results of bar graphs of crosses I and II ? Name the genetic principle illustrated.$
The diagram below shows the distribution of two barnacle species, Chthamalus and Balanus on a rocky sea shore. When Balanus is experimentally removed, Chthamalus expands its range in lower intertidal zone.
Q.30 (a)1 mark $Identify and define the ecological phenomenon demonstrated by this observation.$
OR
Q.30 (a) OR1 mark $State the principle that explains the elimination of one species.$
Q.30 (b)1 mark $Two different species can compete for the same resource. Give another example of it.$
Q.30 (c)2 marks $How do species avoid competition in nature ? Explain with an example.$

Section E

5 marks each

Q.31 (a)5 marks $In angiosperms, the female gametophyte develops from a single cell of megasporangium. (i) Name that cell of megasporangium and describe the sequential changes it undergoes to form a mature female gametophyte. (ii) Draw a well labelled diagram of mature female gametophyte. Label any four parts.$
OR
Q.31 (b)5 marks $Given below are certain situations related to birth control. Analyse each situation carefully and suggest appropriate contraceptive method that could be used. Also explain its mode of action. Situation 1 - To prevent entry of sperm into cervix. Situation 2 - Devices that are inserted by doctors or expert nurses in the vagina. Situation 3 - Effective emergency contraceptive. Situation 4 - Permanent method for male partner. Situation 5 - Surgical method in female to prevent pregnancy.$
Q.32 (a)5 marks $(i) Name the protozoan species that is responsible for causing the most serious and even fatal malarial disease. (ii) Name the host in which the parasite completes its sexual stages and explain the changes taking place. (iii) How does the parasite damage the human body after entering the blood stream ? (iv) Suggest two effective preventive measures to control the spread of this disease in endemic regions.$
OR
Q.32 (b)5 marks $(i) What are bio-fertilizers ? (ii) Name the different types of microorganisms used as bio-fertilizers in organic farming and explain how each contributes to soil fertility. (iii) Write two advantages of using bio-fertilizers over chemical fertilizers.$
Q.33 (a)5 marks $(i) Watson and Crick's discovery of double helical structure was based on which two findings. Also mention the name of the scientists associated with these findings. (ii) Write down the salient features of double helix structure of DNA (any three points).$
OR
Q.33 (b)5 marks $Given below is a stretch of DNA showing the coding strand of structural gene of transcription unit. 5' - ATG ACC GTA TTT TCT GTA GTG CCC GTA CTT CAG GCA TTA 3' (i) Write the corresponding template strand and m-RNA strand that will be transcribed along with its polarity. (ii) If GUA of transcribed mRNA is an intron, then depict the sequence involved in formation of mRNA / mature / processed hnRNA strand : (1) In a bacterium (2) In humans (iii) How many amino acids the resulting polypeptide will have after the process of translation in humans ?$

Section A

1 mark each

Q.11 mark $Perisperm present in seed of black pepper is remnant of$
Tap an option to check your answer.
Q.21 mark $Interferons are most effective in making non-infected cells resistant against the spread of which of the following diseases ?$
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Q.31 mark $Which of the following sacred groves is found in Meghalaya ?$
Tap an option to check your answer.
Q.41 mark $In an ecosystem, different species occupy different levels and vertical distribution of species is found. This is called _________.$
Tap an option to check your answer.
Q.51 mark $Which of the following statements about plasmids is incorrect ?$
Tap an option to check your answer.
Q.61 mark $Which connective tissue connects ovary to pelvic wall and uterus ?$
Tap an option to check your answer.
Q.71 mark $Select the option that shows correct statements : (i) Corpus luteum secretes progesterone. (ii) Only FSH attains a peak level in middle of cycle. (iii) LH surge induces rupture of graafian follicle. (iv) Luteal phase of menstrual cycle is also called proliferative phase.$
Tap an option to check your answer.
Q.81 mark $Which one of the following evidences does not support Darwin's theory of natural selection ?$
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Q.91 mark $Expression of a particular gene helps to identify transformants. What is this gene known as ?$
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Q.101 mark $A DNA molecule is 140 base pairs long. It has 20% thymine. How many guanine bases are present in the molecule ?$
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Q.111 mark $Select the mismatched pair :$
Tap an option to check your answer.
Q.121 mark $Pomato was produced by fusing protoplasts of$
Tap an option to check your answer.
For Questions number 13 to 16, two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) given below :
Q.131 mark $Assertion (A) : Fossils provide direct evidence for evolution. Reason (R) : Fossils help to trace evolutionary relationships among organisms over time.$
Tap an option to check your answer.
Q.141 mark $Assertion (A) : In terrestrial ecosystem much larger fraction of energy flows through grazing food chain. Reason (R) : Grazing food chain may be connected to Detritus food chain at some levels.$
Tap an option to check your answer.
Q.151 mark $Assertion (A) : The milk produced by transgenic cow 'Rosie' was nutritionally more balanced product for human babies than natural cow milk. Reason (R) : It was human protein enriched milk containing human alpha lactaglobulin.$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : Flocs are masses of bacteria associated with fungal filaments in secondary treatment of sewage. Reason (R) : Flocs help in digestion of solid waste by anaerobic respiration.$
Tap an option to check your answer.

Section B

2 marks each

Q.172 marks $A health officer visiting two different regions reported the following symptoms in patients : Region A - Sustained high fever with stomach pain, constipation and loss of appetite. Region B - Inflammation in the lower limbs and genital organs. Name the diseases likely affecting the patients in regions A and B. Write the scientific name of the causative organisms in both the cases.$
Q.18 (a)2 marks $(i) How does a farmer use dormancy of seed to his advantage ? (ii) Differentiate between pea seed and castor seed.$
OR
Q.18 (b)2 marks $Identify the stage of follicle where primary oocyte undergoes first meiotic division. Also mention the products of this division.$
Q.192 marks $Write any two advantages of producing plants by micro-propagation.$
Q.20 (a)2 marks $Mendel published his work on inheritance in 1865, but it remained unnoticed for over three decades. State the reasons why his work was not recognised during his life time. (4 points)$
OR
Q.20 (b)2 marks $What is adaptive radiation ? Give one example from any habitat.$
Q.21 (a)2 marks $(i) What is primary productivity of an ecosystem and how is it expressed ? (ii) Explain the equation given below : NPP = GPP - R$
OR
Q.21 (b)2 marks $Biodiversity conservation is crucial for maintaining ecological balance and ensuring the survival of future generations. Describe four advanced ex-situ methods used for conservation of biodiversity.$

Section C

3 marks each

Q.223 marks $Observe the given picture carefully. A mixture of DNA with fragments ranging from 100 base pairs to 1800 base pairs were separated by electrophoresis on agarose gel with the following arrangement : (a) What result will be obtained in staining with ethidium bromide ? Explain with reasons. (b) The above setup was modified as shown below and a band with 100 base pairs was obtained at X. What changes were made to the previous design to get a band at 'X'. Why did the band appear at 'X' ?$
Q.233 marks $(a) Mention the scientific name of the source plant and the part from which opioids are extracted. (b) How are morphine and heroin related ? Mention the effect each one of them has on human body.$
Q.243 marks $(a) Do all pollen grains remain viable for the same length of time ? Support your answer with two suitable examples. (b) How are pollen grains stored in pollen banks ?$
Q.253 marks $(a) What is pedigree analysis ? Mention its importance in human genetics. (2 pts.) (b) Analyse the following pedigree and write the (i) Pattern of inheritance. (ii) Give one example of disease showing such an inheritance pattern.$
Q.263 marks $(p^2 + 2pq + q^2) = 1$
Q.273 marks $Suggest and describe a technique through which a healthy sugarcane plant can be obtained from virus infected sugarcane plant.$
Q.283 marks $Draw a neat diagram of megasporangium of an angiosperm and label any six parts.$

Section D

The diagram below shows the distribution of two barnacle species, Chthamalus and Balanus on a rocky sea shore. When Balanus is experimentally removed, Chthamalus expands its range in lower intertidal zone.
Q.29 (a)1 mark $Identify and define the ecological phenomenon demonstrated by this observation.$
OR
Q.29 (a) OR1 mark $State the principle that explains the elimination of one species.$
Q.29 (b)1 mark $Two different species can compete for the same resource. Give another example of it.$
Q.29 (c)2 marks $How do species avoid competition in nature ? Explain with an example.$
A student performed some crosses in plants and represented the result in the form of bar graphs as shown below. Each graph displays the phenotypic proportion of the progeny. Study the graphs and answer the questions :
Q.30 (a)1 mark $What can you infer about the genotype of parents in crosses I and II ?$
OR
Q.30 (a) OR1 mark $Which genetic cross is represented by these crosses ?$
Q.30 (b)2 marks $Looking at bar graph of cross III, identify the type of cross performed and its importance in genetics.$
Q.30 (c)1 mark $What conclusion can you draw from the results of bar graphs of crosses I and II ? Name the genetic principle illustrated.$

Section E

5 marks each

Q.31 (a)5 marks $(i) Name the protozoan species that is responsible for causing the most serious and even fatal malarial disease. (ii) Name the host in which the parasite completes its sexual stages and explain the changes taking place. (iii) How does the parasite damage the human body after entering the blood stream ? (iv) Suggest two effective preventive measures to control the spread of this disease in endemic regions.$
OR
Q.31 (b)5 marks $(i) What are bio-fertilizers ? (ii) Name the different types of microorganisms used as bio-fertilizers in organic farming and explain how each contributes to soil fertility. (iii) Write two advantages of using bio-fertilizers over chemical fertilizers.$
Q.32 (a)5 marks $Describe how the lac operon operates both in the presence and absence of an inducer in E.coli.$
OR
Q.32 (b)5 marks $(i) Differentiate between Mendelian and Chromosomal disorders. (ii) Which disorder is known as "Inborn Error of Metabolism" ? Mention its cause and any one symptom. Name the harmful compounds formed.$
Q.33 (a)5 marks $Trace the events from fertilization till implantation of blastocyst in human female. Also mention the site where fertilization takes place.$
OR
Q.33 (b)5 marks $(i) Case studies of some couples are given below. They were not able to have kids even though the parents were not taking any precautions. They also do not wish to adopt a child or take the help of donors. Study these cases and suggest an appropriate Assisted Reproductive Technology that could help them. Case I - Female - Normal Reports Male - Normal sperms but no connection between epididymis and vas deferens. Case II - Female - Normal eggs but Fallopian tube blocked. Male - Normal sperms. Male reports are normal. Case III - Female - Normal Reports. Male - Low sperm count with less motility. (ii) Copper releasing intrauterine devices are very effective and popular contraceptive devices. Name any two copper releasing IUDs. Write two reasons that make them effective contraceptives.$